1. 실습 4주차

2. Exercise Exercise. Consider the following schema:
Suppliers(sid: integer, sname: string, address: string)
Parts(pid: integer, pname: string, color: string)
Catalog(sid: integer, pid: integer, cost: real)
The key fields are underlined, and the domain of each field is listed after the field
name. Therefore sid is the key for Suppliers, pid is the key for Parts, and sid and pid
together form the key for Catalog. The Catalog relation lists the prices charged for
parts by Suppliers. Write the following queries in relational algebra.

3. 1. σcolor=‘red’Parts 2. πpid σcolor=‘red’Parts
<Suppliers>
<Parts>
<Catalog>
Sid
Sname
Address :
Pid
Pname
color :
Sid
Pid
cost :
문제) Find the names of suppliers who supply some red part.
1. σcolor=‘red’Parts
2. πpid σcolor=‘red’Parts
<Parts>
<Parts>
Pid
Pname
color :
p12
red
Pid
Pname
color :
p12
red

4. 3. (πpid σcolor=‘red’Parts) ▷◁ Catalog
문제) Find the names of suppliers who supply some red part.
3. (πpid σcolor=‘red’Parts) ▷◁ Catalog
<Parts>
<Catalog>
Pid
Pname
color :
p12
red
Sid
Pid
cost : s3
p12
Pid
Pname
color :
p12
red
Sid
cost : s3

5. 4. πsid((πpid σcolor=‘red’Parts) ▷◁ Catalog)
문제) Find the names of suppliers who supply some red part.
4. πsid((πpid σcolor=‘red’Parts) ▷◁ Catalog)
5. πsid((πpid σcolor=‘red’Parts) ▷◁ Catalog) ▷◁ Suppliers
Pid
Pname
color :
p12
red
Sid
cost : s3
Pid
Pname
color :
p12
red
Sid
cost : s3
Pid
Pname
color
p12 :
red
Sid
cost s3 :
Sname
Address
Kim :
<Suppliers>
Sid
Sname
Address s3
Kim :

6. 6. πsname(πsid((πpid σcolor=‘red’Parts) ▷◁ Catalog) ▷◁ Suppliers)
문제) Find the names of suppliers who supply some red part.
6. πsname(πsid((πpid σcolor=‘red’Parts) ▷◁ Catalog) ▷◁ Suppliers)
Pid
Pname
color
p12 :
red
Sid
cost s3 :
Sname
Address
Kim :

7. Exercise 1. Find the names of suppliers who supply some red part.
2. Find the sids of suppliers who supply some red or green part.
3. Find the sids of suppliers who supply some red part or are at 221 Packer Street.
4. Find the sids of suppliers who supply some red part and some green part.
5. Find the sids of suppliers who supply every part.
6. Find the sids of suppliers who supply every red part.
7. Find the sids of suppliers who supply every red or green part.
8. Find the sids of suppliers who supply every red part or supply every green part.
9. Find pairs of sids such that the supplier with the first sid charges more for some
part than the supplier with the second sid.
10. Find the pids of parts supplied by at least two different suppliers.
11. Find the pids of the most expensive parts supplied by suppliers named Yosemite Sham.
1번 정답

8. 1. 2. 3. 4. 5. 6.

9. 7. 8. 9.
10.

10. 11.

11. Q & A ?